Optical recording medium, process for manufacturing the same, sputtering target for manufacturing the same, and optical recording process using the same

Abstract

An optical recording medium which comprises a substrate and a recording layer disposed on the substrate, in which the recording layer comprises Ga and Sb, a content of the Sb is 80 atm % to 95 atm % relative to a total content of the Ga and the Sb in the recording layer, and recording and erasing are carried out by a reversible phase change between an amorphous phase and a crystalline phase in the recording layer.

1. An optical recording medium comprising:
 a substrate; and 
 a recording layer disposed on the substrate, 
 
     wherein the recording layer comprises Ga and Sb, a content of the Sb is 80 atm % to 95 atm % relative to a total content of the Ga and the Sb in the recording layer, and recording and erasing are carried out by a reversible phase change between an amorphous phase and a crystalline phase in the recording layer. 
   
   
     2. An optical recording medium according to  claim 1 , wherein the recording and the erasing are carried out by the reversible phase change between the amorphous phase and the crystalline phase in the recording layer, when a laser beam having wavelength of 350 nm to 700 nm is irradiated at a linear velocity (V) one of between more than 3 m/s and 40 m/s or less. 
   
   
     3. An optical recording medium according to  claim 1 , wherein the recording and the erasing are carried out by the reversible phase change between the amorphous phase and the crystalline phase in the recording layer, at a linear velocity of 10 m/s or more. 
   
   
     4. An optical recording medium according to  claim 1 , wherein the total content of the Ga and the Sb is 90 atm % or more in the recording layer. 
   
   
     5. An optical recording medium according to  claim 4 , wherein the total content of the Ga and the Sb in the recording layer is 95 atm % or more. 
   
   
     6. An optical recording medium according to  claim 1 , wherein the content of the Sb is 85 atm % to 95 atm % relative to the total content of the Ga and the Sb in the recording layer. 
   
   
     7. An optical recording medium according to  claim 2 , wherein the optical recording medium comprises:
 the substrate; 
 a first protective layer; 
 the recording layer; 
 a second protective layer; and 
 a reflection layer, 
 
     wherein the first protective layer, the recording layer, the second protective layer, and the reflection layer are disposed on the substrate in this order, and a thickness of the reflection layer satisfies a relation of: 0.10λ or more, when the “λ” expresses the wavelength of the laser beam. 
   
   
     8. An optical recording medium according to  claim 2 , wherein the laser beam has the wavelength of 630 nm to 700 nm. 
   
   
     9. An optical recording medium according to  claim 8 , wherein the optical recording medium comprises:
 the substrate; 
 a first protective layer; 
 the recording layer; 
 a second protective layer; and 
 a reflection layer, 
 
     wherein the first protective layer, the recording layer, the second protective layer, and the reflection layer are disposed on the substrate in this order, and each of a thickness of the first protective layer, a thickness of the recording layer, a thickness of the second protective layer, and a thickness of the reflection layer satisfies the following relations, when “λ” expresses the wavelength of the laser beam;
   0.070λ≦t 1 ≦0.16λ 
   0.015λ≦t 2 ≦0.032λ 
   0.011λ≦t 3 ≦0.040λ 
   0.10λ≦t 4 ; 
 
     wherein “t 1 ” expresses the thickness of the first protective layer, “t 2 ” expresses the thickness of the recording layer, “t 3 ” expresses the thickness of the second protective layer, and “t 4 ” expresses the thickness of the reflection layer. 
   
   
     10. An optical recording medium according to  claim 8 , wherein the thickness of the recording layer is 5 nm to 25 nm. 
   
   
     11. An optical recording medium according to  claim 10 , wherein the thickness of the recording layer is 8 nm to 20 nm. 
   
   
     12. An optical recording medium according to  claim 2 , wherein the laser beam has wavelength of 350 nm to 450 nm. 
   
   
     13. An optical recording medium according to  claim 12 , wherein the optical recording medium comprises:
 the substrate; 
 a first protective layer; 
 the recording layer; 
 a second protective layer; and 
 a reflection layer, 
 
     wherein the first protective layer, the recording layer, the second protective layer, and the reflection layer are disposed on the substrate in this order, and each of a thickness of the first protective layer, a thickness of the recording layer, a thickness of the second protective layer, and a thickness of the reflection layer satisfies the following relations, when “λ” expresses the wavelength of the laser beam;
   0.070λ≦t 1 ≦0.5λ 
   0.015λ≦t 2 ≦0.05λ 
   0.011λ≦t 3 ≦0.055λ 
   0.10λ≦t 4 ; 
 
     wherein “t 1 ” expresses the thickness of the first protective layer, “t 2 ” expresses the thickness of the recording layer, “t 3 ” expresses the thickness of the second protective layer, and “t 4 ” expresses the thickness of the reflection layer. 
   
   
     14. An optical recording medium according to  claim 12 , wherein the optical recording medium comprises:
 the substrate; 
 a reflection layer; 
 a second protective layer; 
 the recording layer; 
 a first protective layer; and 
 a light transmittance layer, 
 
     wherein the reflection layer, the second protective layer, the recording layer, the first protective layer, and the light transmittance layer are disposed on the substrate in this order, and each of a thickness of the reflection layer, a thickness of the second protective layer, a thickness of the recording layer, and a thickness of the first protective layer, and a thickness of the light transmittance layer satisfies the following relations, when “λ” expresses the wavelength of the laser beam;
   0.10λ≦t 4 ≦0.75λ 
   0.011λ≦t 3 ≦0.055λ 
   0.015λ≦t 2 ≦0.05λ 
   0.70λ≦t 1 ≦0.5λ 
   0λ≦t 5 ≦0.6 mm, 
 
     wherein “t 4 ” expresses the thickness of the reflection layer, “t 3 ” expresses the thickness of the second protective layer, “t 2 ” expresses the thickness of the recording layer, “t 1 ” expresses the thickness of the first protective layer, and “t 5 ” expresses the thickness of the light transmittance layer. 
   
   
     15. An optical recording medium according to  claim 12 , further comprising:
 one or more of the recording layers. 
 
   
   
     16. An optical recording medium according to  claim 15 , wherein the optical recording medium includes a first information layer which has one of the recording layers, and a second information layer which has other one of the recording layers in this order, from a direction that the laser beam is irradiated, and a light transmittance of the first information layer is 40% or more with the wavelength. 
   
   
     17. An optical recording medium according to  claim 3 , wherein the recording and the erasing are carried out by the reversible phase change between the amorphous phase and the crystalline phase in the recording layer, at a linear velocity of 14 m/s or more. 
   
   
     18. An optical recording medium according to  claim 17 , wherein the recording and the erasing are carried out by the reversible phase change between the amorphous phase and the crystalline phase in the recording layer, at a linear velocity of 28 m/s or more. 
   
   
     19. An optical recording medium according to  claim 1 , wherein a reflectance (Rg) at an unrecorded space part satisfies a relation of 12%≦Rg≦30%, when a laser beam having wavelength between 350 nm and 700 nm is irradiated. 
   
   
     20. An optical recording medium according to  claim 1 , wherein the optical recording medium has a degree of modulation (M) of 0.4 or more, when the recording is carried out at a linear velocity (V) one of between more than 3 m/s and 40 m/s or less and at wavelength of a laser beam of between 350 nm and 700 nm, and the degree of modulation (M) satisfies a relation of:
     M =( Rg−Rb )/ Rg:   
 
     where “M” expresses the degree of modulation, “Rb” expresses a reflectance at a recording mark of the optical recording medium, and “Rg” expresses a reflectance at an unrecorded space part of the optical recording medium. 
   
   
     21. An optical recording medium according to  claim 20 , wherein the optical recording medium has the degree of modulation (M) of 0.4 or more, when the recording is carried out by an optical lens having NA of 0.60 or more. 
   
   
     22. An optical recording medium according to  claim 20 , wherein the optical recording medium has the degree of modulation (M) of 0.6 or more. 
   
   
     23. An optical recording medium according to  claim 20 , wherein the optical recording medium has the degree of modulation (M) of 0.4 or more, when the recording is carried out at any linear velocity (V) between 10 m/s and 35 m/s. 
   
   
     24. An optical recording medium according to  claim 23 , wherein the optical recording medium has a jitter value of 10% or less, when the recording is carried out at any linear velocity (V) between 10 m/s and 35 m/s. 
   
   
     25. An optical recording medium according to  claim 1 , wherein the recording layer further comprises at least one element selected from Ag, Au, Cu, Zn, B, Al, In, Si, Ge, Sn, Pb, N, P, Bi, La, Ce, Gd, Th, Mg, Co, Mn, Zr, Rh, Se, Fe, and Ir. 
   
   
     26. An optical recording medium according to  claim 25 , wherein the element is at least one selected from Ag, Au, Cu, B, Al, In, Mn, Sn, Zn, Bi, Pb, Ge, Si., and N. 
   
   
     27. An optical recording medium according to  claim 1 , wherein the recording layer comprises an alloy expressed by the following Formula (1);
   GaαSbβXγ  Formula (1) 
 
     where “X” expresses one of an element and a mixture of elements excluding Ga and Sb, “α,” “β,” and “γ” are each expressed in atm %, and each satisfy relations of: “α+β+γ=100,” “5≦α≦20,” “80≦β≦95,” and “0<γ≦10.” 
   
   
     28. An optical recording medium according to  claim 27 , wherein the “X” comprises one of a single element and a mixture selected from Ag, Au, Cu, Zn, B, Al, In, Si, Ge, Sn, Pb, N, P, Bi, La, Ce, Gd, Tb, Mg, Co, Mn, Zr, Rh, Se, Fe, and Ir. 
   
   
     29. An optical recording medium according to  claim 25 , wherein the recording layer comprises Ga, Sb, Bi, and Rh. 
   
   
     30. An optical recording medium according to  claim 29 , wherein the recording layer further comprises one element selected from Cu, B, N, Ge, Fe, and Ir. 
   
   
     31. An optical recording medium according to  claim 25 , wherein the recording layer comprises Ga, Sb, Zr, and Mg. 
   
   
     32. An optical recording medium according to  claim 31 , wherein the recording layer further comprises one element selected from Al, C, N, Se, and Sn. 
   
   
     33. An optical recording medium according to  claim 1 , wherein the optical recording medium comprises:
 the substrate; 
 a first protective layer; 
 the recording layer; 
 a second protective layer; 
 a reflection layer; and 
 a surrounding protective layer, 
 
     wherein the first protective layer, the recording layer, the second protective layer, and the reflection layer are disposed on the substrate in this order, and the surrounding protective layer is disposed on a surface of the reflection layer. 
   
   
     34. A process for manufacturing an optical recording medium comprising the steps of:
 disposing a first protective layer, a recording layer, a second protective layer, a reflection layer in this order on a substrate, so as to manufacture an optical recording medium prior to initial crystallization; 
 irradiating a laser beam having a power density of 5 mW/μm 2  to 50 mW/μm 2  to the optical recording medium prior to initial crystallization, while rotating the optical recording medium prior to initial crystallization and radially moving the laser beam at a constant linear velocity for initial crystallization of 3 m/s to 18 m/s, so as to initially crystallize the optical recording medium prior to initial crystallization and manufacture an optical recording medium, wherein the optical recording medium comprises: 
 a substrate; and 
 the recording layer disposed on the substrate, wherein the recording layer comprises Ga and Sb, a content of the Sb is 80 atm % to 95 atm % relative to a total content of the Ga and the Sb in the recording layer, and recording and erasing are carried out by a reversible phase change between an amorphous phase and a crystalline phase in the recording layer. 
 
   
   
     35. A process for manufacturing an optical recording medium according to  claim 34 , wherein the laser beam has the power density of 15 mW/μm 2  to 40 mW/μm 2 , and the constant linear velocity for initial crystallization is 6 m/s to 14 m/s. 
   
   
     36. An optical recording process comprising the steps of:
 forming a laser beam which reversibly phase changes between an amorphous phase and a crystalline phase in a recording layer which is disposed on a substrate of an optical recording medium, so as to have one of a single pulse and a plurality of pulses; and 
 irradiating the laser beam to the optical recording medium at a linear velocity (V) one of between more than 3 m/s and 40 m/s or less, and at a recording power (Pw) having a power density of 20 mW/μm 2  or more, so as to record in the recording layer, 
 
     wherein the optical recording medium comprises:
 the substrate; and 
 the recording layer disposed on the substrate, wherein the recording layer comprises Ga and Sb, a content of the Sb is 80 atm % to 95 atm % relative to a total content of the Ga and the Sb in the recording layer, and recording and erasing are carried out by a reversible phase change between an amorphous phase and a crystalline phase in the recording layer. 
 
   
   
     37. An optical recording process according to  claim 36 , wherein the linear velocity (V) is one of between 10 m/s and 35 m/s. 
   
   
     38. An optical recording process according to  claim 37 , wherein the laser beam is irradiated, so that a ratio of an erasing power (Pe) to the recording power (Pw) satisfies a relation of:
   0.10 ≦Pe/Pw≦ 0.65: 
 
     where “Pe” expresses the erasing power and “Pw” expresses the recording power. 
   
   
     39. An optical recording process according to  claim 38 , wherein the laser beam is irradiated so as to have a ratio of an erasing power (Pe) to the recording power (Pw) which satisfies a relation of:
   0.13≦ Pe/Pw≦ 0.6: 
 
     where “Pe” expresses the erasing power and “Pw” expresses the recording power.